Q: Last year I planted six 'October Skies' asters in spring, and they did great all year, even through the blistering drought. I liked them so much I planted more in the fall and more this spring. All are doing well except for those I planted last spring. At the end of June, they started browning from the base to the top and ultimately dying. What is even more perplexing is there is a patch 10 feet away doing fine. I'd like to know A.) what is killing them, and B.) would it be unwise to plant?

A: I'd put my money on botrytis stem rot (also sometimes called gray mold or botrytis blight). It's a fairly common soil disease and can strike a lot of plants besides just asters. Soil-borne diseases can take down a plant pretty quick. They just turn brown all over and collapse from the death of the roots. Asters can get another disease called aster yellows and also get attacked by mites, but you'd have seen a longer lead time before death and have seen damage to the foliage, not just a fairly quick and total collapse. The timing also adds up. Botrytis is usually most damaging in late spring. But the big thing is dampness. Wet soil really fuels it. We had plenty of that this spring. I'd guess that maybe you got the disease on that particular batch of plants you planted last spring. Last year's hot, dry weather wasn't as conducive to growing the fungus as this spring's weather. That might explain why just that group was affected. If it is botrytis, it can spread to other asters and other plants. Treating nearby plants with a fungicide can help, but from what I've read, they're not all that effective (not to mention expensive). The best approach seems to be basic plant sanitation, i.e. removing all infected plants and plant parts to limit the spread of the fungal spores.

Dry weather is the best cure. You can help that by not watering the leaves when you water (water the ground) and not overwatering to the point where the soil is soggy. Good drainage in the first place helps, so when you replant, I'd work compost into the area where the asters died and try to raise it up a bit. I'd also switch to a different species, especially ones that aren't as prone to botrytis. Coreopsis and black-eyed susans would be two alternatives. Here's a link to a good web page from Illinois Extension that discusses botrytis, its symptoms, its management and plants that are most susceptible:http://m.extension.illinois.edu/focus/graymold.cfm. Here's also a link to Penn State's disease page on asters that has a good chart on the most common aster diseases: http://extension.psu.edu/plant-disease-factsheets/all-fact-sheets/aster-diseases. To nail down an exact diagnosis of botrytis, Penn State offers free disease testing to home gardeners. You can either take a sample into your local Extension office or mail a sample off to the Disease Clinic at main campus. Here's a link to that site that includes a form to fill out and instructions: http://plantpath.psu.edu/facilities/plant-disease-clinic.